With half of its directors planning to retire as part of the demographic transformation of the profession, the Association of Academic Health Sciences Libraries (AAHSL) undertook a leadership development program to encourage and prepare its future library directors. This article describes the association's multipart program in which each component can stand alone or as a sequence in preparation for a director position. It examines in detail one of the components, a successful mentoring program developed with support from the National Library of Medicine (NLM), the NLM/AAHSL Leadership Fellows Program. The authors describe the methodology and findings of a comprehensive qualitative evaluation study of the Leadership Fellows Program.